I picked up a Walter today and turned him into a puppet. While it seems kind of intuitive, here's what I did:

1. Carefully unstitched the back half of his shirt from his pants (it would benefit from a couple of stitches on either side now to keep them from coming apart further, but I'm not so talented as that)
2. Removed all stuffing from his body (the arms and legs are separate) and the lower half of his head (his "jaw")
3. Trimmed the lower plastic mouth form (it can be brought through the hole you've made) carefully to conform better to the actual lower part of his mouth (it sticks out further, giving him an underbite)

And there you have it! The only challenge is a major one...getting your hand up into the head. Most adult hands won't fit through his neck, but I was able to manipulate the mouth by putting my middle and ring fingers into the upper half (between the stuffing and the roof of his mouth) and my index finger and pinky in the lower part (your thumb stays in the body). A little uncomfortable, but sort of workable...and your index finger pokes through his chin kind of like the thumb on classic Kermit! But the best part is that he displays much better I think as a puppet than as a stuffed figure. Anyone else been inclined to try it??

Here's a photo of the above Walter...positioned on a water bottle alongside the unaltered plush, and also on my hand (fingers only...the head's too small for my whole hand). In just ten minutes you too can have a cool Walter puppet...or at least a more realistic display!

I did the same thing a while back. But I just trimmed the plastic of the bottom of the mouth and took some of the stuffing out of his head. Looks MUCH better. A big part of why his mouth is so weird is how much stuffing they cram into his head.